Slip measurement and vehicle control for leg/wheel mobile robots using caster type odometers

In this paper, we propose a velocity control method for leg/wheel type robots by using tire side slip angle and tire slip ratio. Side slip angle and slip ratio is measured by caster type odometers which are comprised of directional sensors and travel distance sensors. The odometer system has redundant four encoders to measure three dimensional velocities: planar two dimensional and rotational movements. We reduce the error between target velocity and actual velocity by feedback control based on both tire slip angle and slip ratio. This method can improve stability and accuracy of movement of vehicles. The experimental vehicle is an omnidirectional vehicle which has legs comprised of three joints. Experimental results of circular trajectory running show effectiveness of the proposed control method.